The Ancient Life History of the Earth eBook

Strata of Upper Eocene age occur in North America
at Vicksburg, Mississippi, and are known as the Vicksburg
series. They consist of lignites, clays,
marls, and limestones. Freshwater deposits of
Eocene age are also largely developed in parts of the
Rocky Mountain region. The most remarkable fossils
of these beds are Mammals, of which a large number
of species have been already determined.

LIFE OF THE EOCENE PERIOD.

The fossils of the Eocene deposits are so numerous
that nothing more can be attempted here than to give
a brief and general sketch of the life of the period,
special attention being directed to some of the more
prominent and interesting types, amongst which—­as
throughout the Tertiary series—­the Mammals
hold the first place. It is not uncommon, indeed,
to speak of the Tertiary period as a whole under the
name of the “Age of Mammals,” a title at
least as well deserved as that of “Age of Reptiles”
applied to the Mesozoic, or “Age of Molluscs”
applied to the Palaeozoic epoch.

As regards the plants of the Eocene, the chief
point to be noticed is, that the conditions which
had already set in with the commencement of the Upper
Cretaceous, are here continued, and still further
enforced. The Cycads of the Secondary period,
if they have not totally disappeared, are exceedingly
rare; and the Conifers, losing the predominance
which they enjoyed in the Mesozoic, are now relegated
to a subordinate though well-defined place in the
terrestrial vegetation. The great majority of
the Eocene plants are referable to the groups of the
Angiospermous Exogens and the Monocotyledons; and
the vegetation of the period, upon the whole, approximates
closely to that now existing upon the earth.
The plants of the European Eocene are, however, in
the main most closely allied to forms which are now
characteristic of tropical or sub-tropical regions.
Thus, in the London Clay are found numerous fruits
of Palms (Napdites, fig. 213), along with various
other plants, most of which indicate a warm climate
as prevailing in the south of England at the commencement
of the Eocene period. In the Eocene strata of
North America occur numerous plants belonging to existing
types—­such as Palms, Conifers, the Magnolia,
Cinnamon, Fig. Dog-wood, Maple, Hickory, Poplar,
Plane, &c. Taken as a whole, the Eocene flora
of North America is nearly related to that of the
Miocene strata of Europe, as well as to that now existing
in the American area. We conclude, therefore,
that “the forests of the American Eocene resembled
those of the European Miocene, and even of modern America”
(Dana).

[Illustration: Fig. 213.—­Napadites
ellipticus, the fruit of a fossil Palm. London
Clay, Isle of Sheppey.]